Aseptically working packaging machine and method for pre-sterilizing them

ABSTRACT

The present invention is concerned with aseptically operating packing machines and with a process for the pre-sterilization thereof. For jointly spraying steam and sterilizing agent at a single point into a sterile air supply channel which terminates in the sterile chamber of the packing machine, a mixing nozzle is arranged in the air supply channel directly downstream behind a sterile air filter. For pre-sterilizing purposes the treatment tools possibly still in hot condition and contained in the sterile chamber, prior to commencement of the pre-sterilizing process, are brought to a temperature below  120 ° C. The mixture of water vapor and sterilizing agent is effectuated by means of the mixing nozzle to which both components are supplied. The steam supply to the nozzle is effectuated by a pressure relief valve followed by a regulation of the steam volume, while the supply of sterilizing agent to the nozzle is effectuated from a stock of sterilizing agent held at a constant pressure. During the start-up phase of the pre-sterilizing process the sterile air supply for the purpose of a partial return flow generation of the discharged mixture of water vapor/sterilizing agent upstream toward the sterile air filter is discontinued temporarily.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention is concerned with aseptically operatingpacking machines and a process for the pre-sterilization thereof. Theterm “packing machines” in the present instance, in particular, refersto two types of machines, to wit, on the one hand, machines wherein theweb of packing material of suitable thermoplastic plastic or plasticcompound foil, by deep drawing, is cyclically fed through the machine,preheated, heated molded by deep-drawing to form containers that areloaded and then sealed by a cover foil, and, on the other hand, machinesforming so-called tubular bags wherein the web of packing material isalso cyclically molded to form a hose to be longitudinally sealed, withthe hose being sealed at the bottom by a transverse seal, then filledand, after withdrawal, closed at the top equally by a transverse sealand then severed from the hose automatically supplied.

[0003] 2. Description of the Prior State of Art

[0004] The package of foodstuffs and semi-luxuries in containerscorrespondingly molded from webs of packing sheet is required to be insterile, i.e. substantially aseptical condition. For that purpose,aspetically operating packing machines of the afore-mentioned type areavailable in the art that have sterile spaces in which are provided theprocessing or treatment tools for the web of packing foil. Indeep-drawing packing machines the processing elements are pre-heatingplates, the deep-drawing tools and the filling and sealing elements forthe cyclically passing web of packing sheet, while in tubular bagpacking machines the said processing elements form the tubular moldingand loading stations including the heatable longitudinally sealing toolsand all guiding elements for the web of packing sheet located ahead ofthat station. During operation at a slight excess pressure, sterile airis continuously supplied to the sterile spaces of such machines tomaintain the sterile atmosphere clear of re-contamination duringoperation, insuring that at predetermined points of the sterile spacesthe sterile air also can again flow out of the sterile space. After anoperational close-down of machines of the afore-described type, be itfor shift end reasons or otherwise, it will be necessary to render theaseptic spaces and the afore-mentioned processing tools containedtherein again sterile prior to re-putting them into operation.

[0005] DE 24 35 037 C2 discloses, for example, a process ofpre-sterilizing the surfaces of items wherein the surfaces, prior tosupplying hydrogen peroxide (so-called peroxide) as the sterilizingagent, initially, are treated with a flow of water vapor to regularlyheat all surfaces to be treated. It is only after such a heating processthat peroxide is admixed to the steam, thereby additionally raising thetemperature thereof. After having been so pre-sterilized thesubsequently introduced peroxide is washed away by non-heated sterileair. As the desired heating of the surfaces, inevitably, involveswetting of the surfaces with condensate containing no sterilizing agentit will have to be left unconsidered to what extent the mixture ofsterilizing agent and steam supplied in a second step can take fulleffect. As, moreover, such sterile spaces and the processing toolscontained therein are not clear of corners or gaps, it is unavoidable,that during pre-steaming, such corners or gaps cannot be reached anylonger by the peroxide subsequently admixed to the steam because theyare quasi already blocked by pure steam condensate, i.e. by water. Aparttherefrom this process does not safeguard that the germs protected bythe condensate drops are reached by the sterilizing agent at therequired concentration because the sterilizing mixture is preventedtherefrom due to the condensate already deposited. Another disadvantageresides in that the surfaces to be sterilized are so heated by the steamand by subsequent additional steaming, while adding sterilizing agent,that the mixture of steam/sterilizing agent no longer is safelycondensed on all surfaces. The dilemma is that the chemical reactivityof the condensing (i.e. liquid) sterilizing agent, on the one hand, isenhanced, while on the other hand, in view of the destruction ofmicro-organisms and spores, the chemical reactivity markedly decreasesonce the sterilizing agent no longer is in liquid form but passes to thegaseous (vaporous) state.

[0006] DE 197 26 222 A1 is equally concerned with the question ofpre-sterilization especially in connection with a mechanism specificallydesigned herefore and provided with a so-called reversible blower inorder to have gaseous or vaporous sterile agent flow through the sterilespaces along with the tools contained therein in two differentdirections. Apart from the reversible blower required herefore, thismechanism involves out-of-proportion mechanical efforts, i.e. a largenumber of conduits and a substantial number of re-switchable valvesrequiring corresponding valve control means. Moreover, in theafore-described mechanism the sterilizing agent is introduced betweentwo filters involving the danger of that the fine filter coupled to theblower is decomposed. Also, it will have to be left unconsidered howmuch of the sterilizing agent is retained by the filter or is alreadychemically reacted in the filter material so that it does not or not intime reach the tunnel or tubing area to be pre-sterilized during theproduction phase.

[0007] A pre-sterilization of a sterile tunnel is also provided with anarrangement according to U.S. Pat. No. 3,820,300, wherein a liquidsterilizing agent is injected into the sterile air supplied prior tocommencement of the actual packing processing. After completion of thepre-sterilization, the injection of the sterilizing agent is simplydiscontinued. The supply of the mixture consisting of sterile air andsterilizing agent as well as the subsequent exclusive supply of sterileair are effectuated in a way similar to DE 197 26 222 A1 via a complexmultiplicity of individual nozzles distributed throughout the sterilespace, which, individually, are difficult to control and which areconnected to so-called “distributors”. Corners or gaps which are thepreferred places, as mentioned before, for bacteria invasions, cannot bereached thereby because the sterile air being the carrier of theinjected sterilizing agent has no reason to penetrate such corners orgaps in communication with the atmosphere, let alone that a suppliedgaseous sterilizing agent formed of the mixture of sterile air andsterilizing agent has, as mentioned before, a lower sterilizing effectthan a condensing (i.e. locally liquid) sterilizing agent.

SUMMARY OF THE INVENTION

[0008] In the light of the afore-going it is the object of the inventionnot only to carry out the required pre-sterilization in a satisfactoryway but also to minimize the mechanical efforts, using the supply ofsterilizing air anyway required for normal package operations as acontrollable conveying means for a mixture of steam and sterilizingagent supplied at a mixture ratio predetermined from the very start,insuring at the same time that the said total mixture will find suchtemperature conditions in the space to be sterilized and on theprocessing tools contained therein, that, on the one hand, an unimpededcondensation of the mixture of steam and sterilizing agent on allsurfaces and in the gaps and crevices be safeguarded and, on the otherhand, the temperature-dependent chemical reactivity of the sterilizingagent be optimally secured by a defined temperature regulation.

[0009] Proceeding from the traditional practice according to which priorto putting into operation the packing machine concerned, a sterilizingagent, such as hydrogen peroxide or the like, is sprayed into thesterile space and, after the said pre-sterilization, sterile air, duringthe operative period or during the packing process, is permanentlysupplied to and discharged from the sterile chamber, the probleminvolved with the pre-sterilization process according to the inventionhas been solved by the following process steps:

[0010] a) the treatment elements in the sterile chamber which mightstill be hot, prior to commencing the pre-sterilization process, arebrought to a temperature below 120° C.;

[0011] b) the mixture of water vapor being the carrier medium, andsterilizing agent is effectuated by means of a nozzle to which bothcomponents are supplied;

[0012] c) the mixture of water vapor and sterilizing agent is introducedat a single point, downstream, directly behind the sterile filter in thesame direction as the incoming sterile air serving as the carriermedium, directed toward the sterile chamber;

[0013] d) the steam supply to the nozzle is effectuated by a pressurerelief valve and a subsequent means regulating the steam volume, whereasthe supply of sterilizing agent to the nozzle is from a stock ofsterilizing agent held at a constant pressure, and

[0014] e) during the pre-sterilizing start-up phase, the supply ofsterile air is temporarily discontinued for the generation of a partialreturn flow of the discharged mixture of water vapor and sterilizingagent, upstream, toward the sterile air filter.

[0015] The aseptically operating packing machine still comprises, as itdid in the past, a processing track furnished with elements for treatingthe web of packing foil in a sterile chamber partially open toward theatmosphere and provided with elements for the supply of sterile agentand with a nozzle for a generator of sterile air furnished with blower,heater and sterile filter. In the practice of the invention, a packingmachine of the afore-described type, for pre-sterilizing purposes, isfurnished with the following:

[0016] Downstream, directly behind the sterile air filter, is disposed,within a sterile air passageway terminating in the sterile chamber, amixing nozzle connected to conduits for feeding steam and sterilizingagent, which is arranged toward the direction of the termination of thesterile air passageway in the sterile chamber, with a tank allocatingthe sterilizing agent held at a constant pressure and provided with apressure relief valve disposed ahead thereof being disposed in thesterilizing agent supply line, and a pressure relief valve includingmeans for regulating the steam volume being provided in the steam supplyconduit.

[0017] In the light of the afore-going, the invention is not restrictedto the simple feature of reducin a multiplicity of spraying portsaccording to DE 197 26 222 A1 and U.S. Pat. No. 3,820,300 to one singleport, as this measure alone would not achieve a satisfactorypre-sterilization of the entire sterile chamber; the afore-mentionedadditional process features and objects will be necessary, as on the onehand, a special arrangement (utilization of the sterile air flow) and adirectional orientation of the mixing nozzle have proved to be necessaryand, on the other hand, a mixing ratio of steam and sterilizing agentinsuring a satisfactory germ destruction will have to be taken intoconsideration. In addition, due to the arrangement of the mixing nozzledirectly downstream behind the sterilizing air filter, the latter ismost easily and controllably incorporated into the pre-sterilizingprocess in that the sterile air blower is simply turned off for a shortperiod of time. Moreover, the feature of the temperature decrease of theelements of treatment insures that the subsequently introduced mixtureof sterilizing agent can condense throughout the place, including allcorners and gaps without being affected by moisture otherwise alreadycontained therein. Preferably and with advantage, the temperature isdecreased to a value below the condensation temperature of the mixtureof steam and sterilizing agent.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The process of the invention and aseptically operating packingmachines to be pre-sterilized thereby, including advantageousembodiments thereof, will now be described in greater detail withreference to the graphical illustration of some forms of embodiment,wherein:

[0019]FIG. 1 schematically shows a side and sectional view of a packingmachine designed according to the invention for molding, filling andsealing of containers in the form of beakers;

[0020]FIG. 2 schematically shows a sectional view of the nozzle formixing steam and sterilizing agent;

[0021]FIG. 3 schematically shows a cross-sectional view of the sterilechamber of the packing machine according to FIG. 1; and

[0022]FIG. 4 shows side and sectional views of a packing machinedesigned according to the invention for making tubular bags.

DESCRIPTION OF PREFERRED FORMS OF EMBODIMENT

[0023] Referring to the drawings, FIG. 1 shows an aseptically operatingdeep-drawing packing machine for making and filling of beakers, theprocessing track VS of which for the web of packing foil PB is coveredby a so-called sterile tunnel 18 externally confining the sterilechamber 1 and including a sterile air supply channel 2 and containingthe schematically shown stations 100, 101, 102, 103 for preheating offoils, molding, loading and sealing the beaker-type containers B.Concerning such a machine, reference is made to EP 0 727 357 A2.

[0024] To comply with the requirement of the process of the inventionfor pre-sterilizing the sterile chamber 1, namely to introduce thesterilizing agent mixed with water vapor as the carrier medium, at asingle point, downstream, behind the sterile air filter 6 from thesterile air supply area toward the sterile chamber 1, effectuating thesteam supply through a pressure relief valve 9 for adjusting a constantsteam pressure followed by a regulation of the steam volume, and to feedthe sterilizing agent usually dissolved in a 35% aqueous solution at aconstant pressure to the mixing point, it is important to the machine toprovide, downstream, directly behind the sterile air filter 6, withinthe sterile air channel 2 terminating in the sterile chamber 1, a mixingnozzle 3 connected to a steam- and a sterile agent-carrying conduit 8,11 and so arranged that it points toward the termination 2′ of thesterile air passageway 2 opening in the sterile chamber 1. A tank 12allocating the sterile agent having a pressure relief valve 13 coupledahead thereof and being held at a constant pressure is disposed in thesterile-agent-feeding conduit 1, while a pressure relief valve 9 havinga steam volume regulator 10 coupled therebehind is provided in thesteam-feeding conduit 8.

[0025]FIG. 3 is a cross-sectional view of a so-called semi-tunnel 18which confines the sterile chamber 1. FIG. 3 also illustrates that thesterile chamber 1 is partially open toward the atmosphere, specificallyat the bottom edges 18′ of the sterile tunnel 18. The said partiallyopen condition toward the atmosphere enables the permanent off-flow ofthe sterile air flowing at a slight excess pressure in the sterilechamber 1 during the normal packing operation as indicated by arrows P,but also of the mixture of steam and sterilizing agent during thepre-sterilization presently of interest.

[0026] The mixing nozzle 3 in reference to FIG. 2 is designed in theform of a dual nozzle 3′, with the so-called nozzle stock 3″ serving forintroducing the sterile agent which is supplied, for example, at a 35%concentration in aqueous solution as hydrogen peroxide and is sprayedinto the steam jet discharged from the conduit 3′″ as a flow hose,thereby being intensively mixed with the steam which along with thesterile air carries the sterilizing agent into the whole of the sterilechamber 1, distributing it therein, with the steam along with thesterilizing agent depositing or condensing even in corners and gussetsalong the walls of the sterile chamber 1 and the tools of treatmentcontained therein.

[0027] During the pre-sterilizing start-up phase, the supply of sterileair for the partial return flow generation of the discharged mixture ofsterilizing agent toward the upstream sterile filter 6 is temporarilydiscontinued for a predetermined period of time to also reach, in aneasy way, during the pre-sterilizing process, the sterile air filter 6.The phrase “temporarily discontinued for a predetermined period of time”refers to, for example, between 15 and 30 seconds out of a totalpre-sterilization duration of, for example, between about 3 and 5minutes. For that purpose, the arrangement is so designed that,downstream, at a small distance behind the mixing nozzle 3, a flowresistor (drag) 15 is arranged in the form of a channel buckling asshown on the sterile air feeder 2 conically constricting to that extent.The drive 4′ of the blower 4 in a sterile air generator 7 comprising apre-filter 6′ and an air heater 5 for such a temporary interruption ofthe sterile air supply is provided with an adjustable timer 16.

[0028] It is at least during the afore-mentioned pre-sterilizingstart-up phase that also the sterile filter 6 on the flow side, issprayed with sterilizing agent, for which purpose a sterile agent nozzle17 is arranged ahead of the sterile filter 6 at the in-flowing sidewhich, as shown in FIG. 1 in dash-dotted lines, via the tank 12allocating the sterilizing agent, is in communication with a conduit17′.

[0029] To avoid a damming up of heat or the formation of a heat bubblein the area of the web pre-heating elements 19 in the machine accordingto FIG. 1, which would affect the in-flow of the sterilizing agent/steammixture in the in-flow-sided area 1′ of the sterile chamber 1, thetemperature thereof, preferably, is held below 120° C. i.e. at atemperature level preferably of between 40 and 80° C. Should thepre-sterilization have to be effectuated after a temporary interruptionof the operation of the machine, whereafter the pre-heating elements 19are still relatively hot, the pre-sterilization would be initiated onlyafter the said elements having cooled down accordingly. This process viatemperature sensors anyway provided in this area with machines of thistype could be monitored and supervised by the machine control.

[0030] The same applies to the packing machine shown in FIG. 4 which isa tubular bag making machine. The heatable elements which in thatembodiment will have to be cooled, i.e. temperature-regulated, forpre-sterilizing purposes, are the elongated seal jaws 20 by way of whichthe tube 22 of the web of packing foil molded on the forming tube 21 islongitudinally sealed. As the way of operation of tubular bag producingmachines of this type is adequately known in the art, no detaileddescription thereof is required. Incidentally, in respect ofcorresponding elements of a tubular bag producing machine the samereference numerals have been used as in the deep-drawing packing machinedescribed in FIG. 1.

[0031] The afore-mentioned temperature regulation as well as all othercontrolling or regulating requirements can be part of a general control(not shown in any detail) of the packing machine in question,irrespective of whether or not it is a machine according to FIG. 1 orFIG. 4.

[0032] Also, the pre-sterilizing process is identical in both caseswhich, in summary, is carried out in a preferred form of embodiment asfollows:

[0033] The tools of treatment possibly still hot as contained in thesterile chamber, prior to commencement of the pre-sterilizing process,by cooling down, are brought to a temperature below 120° C., i.e. to atemperature of the mixture of steam and sterilizing agent below the dewpoint, preferably to between 40-80° C. In the event that the machine hasbeen cooled off due to an extended stand-still period, the heater of thepreheating elements 100 or of the elongated seal yaws 20 is turned onuntil the latter have reached this temperature.

[0034] The mixture of water vapor and sterilizing agent (hydrogenperoxide) is effectuated directly in the mixing nozzle 3 to which bothcomponents are supplied; the water vapor/sterilizing agent is introducedat one single point within the sterile air supply channels 2 downstreamdirectly behind the sterile filter 6 in the same direction as thepreviously switched-on and inflowing sterile air toward the sterilechamber 1. To insure a thorough mixture of steam and sterile agent, thesterilizing agent is centrally introduced into the water vapordischarged in the form of a hose. To further enhance the mixture, theentire flow of sterile air, steam and sterilizing agent can beaccelerated by conically constricting the channel 2 leading to thesterile chamber 1, resulting in a higher turbulence of the flow.

[0035] The steam supply to the nozzle is through a pressure relief valveand a means regulating the steam volume as coupled thereto, while thesupply of the sterilizing agent to the nozzle is from the stock ofsterilizing agent held at a constant pressure, or from the allocatingtank 12 containing the amount of sterile agent required forpre-sterilizing purposes. The said pressure and volume regulation ofsteam and sterilizing agent is important to satisfy the conditions andrequirements to insure a faultless pre-sterilization.

[0036] During the start-up pre-sterilizing phase the sterile air supplyfor a short period of time of between 15 to 30 seconds is discontinuedto thereby cause the discharged mixture of steam and sterilization agentto flow back to a certain extent toward the sterile air filter 6,equally exposing the latter to the sterilizing agent.

[0037] Moreover, also the sterile filter 6, at least during thepre-sterilizing start-up phase, at the air in-flow side, is equallysprayed by sterilizing agent.

[0038] As it can be proceeded from the assumption, irrespective ofwhether the pre-sterilization to be effectuated is preceded by anextended standstill period or only by a short-time temporaryinterruption, that some moisture regularly deposits on the walls of thesterile chamber or on the treatment tools, which, as mentionedhereinbefore, would affect the desired condensation of the mixture ofsteam/sterilization agent, advantageously, prior to commencement of theactual pre-sterilizing process, the sterile chamber and the treatmenttools contained therein are dried by the supply of sterile air suppliedthrough the sterile filter, with the sterile air, for drying, beingsupplied at a temperature in the order of between 40 and 80° C., forwhich purpose the sterile air generator 7 is furnished with acorrespondingly adjustable heater 5.

[0039] Along with the pre-drying and cooling or heat-up period regulatedtemperature) of the treatment tools, the whole of the pre-sterilizationtakes relatively little time, i.e. about 12 to 20 minutes only,depending on the type and size of the machine, whereupon, by maintainingthe sterile air supply but discontinuing the supply of steam andsterilizing agent, the sterile chamber 1 is blown, dried whereafter thepacking machine is conventionally put into operation.

1. An aseptically operating packing machine, comprising a processingtrack furnished with tools for treating the web of packing sheet, withina sterile chamber partially open toward the atmosphere and provided withelements for supplying sterilizing agent, and a nozzle for a sterile airgenerator provided with a blower, a heater and a sterile air filer,wherein arranged, downstream, directly behind the sterile air filter,within an air channel terminating in the sterile chamber is a mixingnozzle connected to a steam- and a sterile agent-carrying conduit andwhich is disposed to point in the direction of the termination of thesterile air channel in the sterile chamber, and wherein a tank forallocating the sterilizing agent held at constant pressure by a pressurerelief valve coupled ahead thereof is arranged in the sterilizing agentsupply conduit while a pressure relief valve including a steam volumeregulator coupled therebehind is arranged in the steam supply conduit.2. The machine according to claim 1, wherein the mixing nozzle isdesigned in the form of a dual nozzle with a central nozzle stock andthat connected thereto is the sterilizing agent-carrying conduitbranching from the allocating tank.
 3. The machine according to claim 1,wherein disposed downstream and at a space behind the mixing nozzle,within the sterile air channel is a flow resistor (drag), such as abuckling, an annular stop, a channel constriction or the like.
 4. Themachine according to claim 1, wherein the drive of the blower isprovided with an adjustable timer.
 5. The machine according to claim 1,wherein arranged at the in-flow side, ahead of the sterile filter, is anozzle for the sterilizing agent, which via conduit is in communicationwith the tank allocating the sterilizing agent.
 6. A process forpre-sterilizing sterile spaces of aseptically operating packing machinesaccording to claim 1, wherein prior to commencement of the operation ofthe packing machine concerned, a sterilizing agent mixed with watervapor as the carrier medium, preferably water-dissolved hydrogenperoxide, is sprayed with the web of packing sheet introduced, into thesterile chamber partially open toward the atmosphere and held at aslight excess pressure and containing the elements for treating the webof packing sheet, with sterile-filtered sterile air as a conveying meansbeing supplied during the pre-sterilizing process, characterized by thefollowing process steps: a) the treatment tools still hot and containedin the sterile chamber, prior to commencement of the pre-sterilizingprocess, are brought to a temperature below 120° C.; b) the mixture ofwater vapor and sterilizing agent is effectuated by means of a nozzle towhich both components are supplied; c) the water vapor/sterilizationmixture is introduced at a single spot downstream directly behind thesterile filter in the same direction as the in-flowing sterile airtoward the sterile chamber; d) the steam supply to the nozzle iseffectuated by a pressure relief valve followed by a subsequentregulation of the steam volume, while the supply of sterilizing agent tothe nozzle is effectuated from a stock of sterilizing agent held at aconstant pressure; and e) during the pre-sterilizing start-up phase thesterile air supply for the purpose of a partial return-flow generationof the discharged mixture of water vapor/sterilizing agent upstreamtoward the sterile air filter is temporarily discontinued.
 7. Theprocess according to claim 6, wherein the sterilizing agent is centrallysprayed into the water vapor discharged in the form of a hose.
 8. Theprocess according to claim 6, wherein at least during thepre-sterilizing start-up phase also the sterile filter, on the airin-flow side, is sprayed by sterilizing agent.
 9. The process accordingto claim 6 wherein the mixture of water vapor, sterilizing agent andsterile air, prior to entrance into the sterile chamber, is guidedthrough a constricted flow section.
 10. The process according to claim6, wherein the sterile chamber inclusive of the elements for treatingthe web of packing sheet, for pre-sterilization, are adjusted to atemperature below the condensation temperature of the mixture ofsteam/sterilizing agent, preferably to between 40 and 80° C.
 11. Theprocess according to claim 6, wherein prior to commencement of theactual pre-sterilization, the sterile chamber along with the treatmenttools contained therein are dried and temperature-regulated by thesupply of sterile air supplied through the sterile filter.
 12. Theprocess according to claim 11, wherein the sterile drying air issupplied at a temperature in the order to between 40 and 80°.